Means for distributing and circulating liquid material



J1me 1941- F. G. GARRISON ETAL 2,244,636

MEANS FOR DISTRIBUTING AND CIRCULATING LIQUID MATERIAL Filed Dec. 24,1938 2 Sheets-Sheet l Riot-Rm GGA/m/sav 51 AL F/PED W CHR/STf/VSOM June10, 1941. 2,244,686

MEANS FOR DISTRIBUTING AND CIRCULATING LIQUID MATERIAL F. G. GARRISONETAL Filed Dec. 24, 1938 2 Sheets-Sheet 2 F/MDER/c G. GA/m/so/v d A4FRED W CHR/STIF/VS 0,

Patented June 10, 1941 MEANS FOR DISTRIBUTING AND CIRCULAT- ING LIQUIDMATERIAL Frederic G. Garrison, Birmingham, and W. Christensen, Detroit,Mich alsignors toBinks Manufacturing Oompany, Chicago, 111., acornotation of Delaware Application December :4, 1938, Serial No.247,685

3 Claims. (01. 91-45) The present invention relates to systems fordistributing fluidal material, including various coating materials, suchas paints, enamels, lacrulers, or the like, and has reference moreparticularly to a system of the circulating type.

Coating materials are supplied under pressure through pipe linesextending along stations where the material is applied to the objects atthe stations, as by means of spray guns, there being a pipe line foreach character of material, and a spray gun at each station for eachpipe line. The spray guns are usually connected by supply ducts, such ashoses, to the pipe lines at the stations. At such times as when any ofthe spray guns are not being operated (to spray) the material in thesupply duct to such gun remains dormant and there is a settling of thepigment or like particles thus forming a sediment. When next the gun isput into operation there is at first a spraying of material of impropercharacter or condition, and if applied immediately to the surface of theobject to be coated or treated, the lob is spoiled. To avoid this, it isnecessary to initially project the material to one side until the ductis cleared oi the dissociated components of the material therein beforethe proper material arrives at the gun, thus causing a waste of materialand loss of time. Moreover, just when the improper material is clearedand the proper material arrives at the gun involves an element ofjudgment on the part of the workman, which is very uncertain andinaccurate.

The present invention comprehends the-provision of a novel means .fordistributing the material with a constant circulation of the material sothat at any and every point of the system the material is homogeneousand of correct condition and character for immediate use, without anywaste, at any instant the gun is to he operated.

The circulating and the maintaining of. the proper condition of thematerial continue regardless of whether or not the gun is beingoperated.

More particularly, each pipe line is in the form of a main circuitcomprising a supply main or circuit portion and a return main or circuitportion, with regulating valves for sustaining the proper pressures inthe circuit portions as also to maintain a circulating flow of thematerial in the hue. Also, for each gun at each station for each linethere is a shunt or cross-circuit wherein there is a continual flow ofthe material from the station point of the supply circuit portion to thecorresponding point of the return circult portion and by way of the gun,together with regulating means for sustaining the predetermined pressureat the gun and for maintaining the flow of material in the crosscircuit. By keeping the material in motion or movement in these ways, ithas no chance to settle and form any sediment, and it is always inproper condition for use at any instant when call is made therefor atthe gun.

The invention also comprehends novel regulating means connected in thesystem for sustaining the predetermined pressures therein and formaintaining a circulation as explained herein.

Other objects, advantages, capabilities, features, or the like arecomprehended by the invention as will later appear and as are inherentlypossessed by the invention.

Referring to the drawings:

Fig. 1 is a diagrammatic view of the circulating distributing system;

Fig. 2 is a view partly in elevation and partly in section, on anenlarged scale, of the by-pass circulating connection to the spray gun;

Fig. 3 is a view in elevation with parts shown in section 01 a pressurecontrol unit in each cir=- culating b -pass;

Fig. 4 is a fragmentary sectional view, on an eniarged scale, of theorifice part of the pressure control unit shown in Fig. 3;

Fig. 5 is a sectional view, on an enlarged scale, of a pressureregulator connected in each circu lating by-pass to each spray gun;

Fig. 6 is a sectional view on an enlarged scale, oi a modulating'valvefor regulating the pressures in. each circuit on both sides of. thevalve, such as on the feed or supply side and the return side;

Fig. 7 is a fragmentary part sectional view, on an enlarged scale, ofthe valve part of the modulating valve;

Fig. 8 is a bottom plan view of the means shown in Fig. 7:

Fig. 9 is a view similar to Fig. 'l of an alternative form of valvemeans;

Fig. 10 is a fragmentary diagrammatic view of part of the system showingthe use of heating means for heating the material in the cross-circuitsbefore the material proceeds to the spray gun; and

Fig. 11 is a similar view showing an alternative construction at the endof the system where the material passes from the supply circuit portionto the return circuit portion and using a control valve of the pressurereducing type for maintaining a uniform pressure on the discharge sidethereof and in the return circuit portion.

Referring more in detail to the drawings, the diagram of Fig. 1 showsschematically a circuit illustrative of any number of circuits, eachalike and each circulating a liquid or similar material of givencharacter, such as a paint of a certain color, or other characteristic.Each circult comprises a main feed pipe line I and a main return pipeline 2.

The feed line I is connected by way of a suitable filter 3 and a pumpdischarge main 4 to a suitably operated pump 5. The pump has an intake'6 connected to the lower end of one or more material containers 1. Aby-pass pipe 8 may be connected to the pump discharge pipe 4 and thefeed main I to by-pass the material whenever it is necessary to cleanthe filter.

From the pump discharge 4 ms 2. feed back pipe 9 by way of a modulatingvalve In to and into the upper part of the tank 1, for the feedback orrecirculation of the material in excess of that needed in the main lineI, the modulating valve I being so adjusted as to maintain a. givenpressure in the main line I and also to vary the surplus return orfeed-back flow of material to the tank 1 inversely with the demand madeon the main line I. There is also connected a relief circuit II with asuitable relief valve I2 between the pump discharge 4 and the tank 1 sothat should the pressure increase to an unsafe point, the material willbe released to the tank 1 by the opening of the relief valve.

Each container 1 has a suitable agitator (not shown) operated by asuitable motor I3 on the container for constantly maintaining thematerial in homogeneous condition. The return line '2 is connected byway of valved pipes I4 to the upper part of the tanks 1. At the end ofthe feed line circuit portion I and at the beginning of the return linecircuit portion 2 is connected a modulating valve I5 which may be soadjusted as to maintain the desired pressures in the feed main I and thereturn main 2 by automatically regulating or varying the flow ofmaterial from the feed to the return main so that there will bemaintained a continual flow of material in the circuit under allconditions of demand on the main circuit portion I, it being importantthat there be no cessation of circulation in the circuit. While amodulating valve I5 is shown, it is to be understood that in lieuthereof an orifice means, such as is shown in Fig. 4 and laterdescribed, may be used, particularly when there is no great fluctuationin pressure in the main circuit portion I, so long as there is always aflow in the circuits so as to maintain a con-- tinual circulation of thematerial, and for the purpose of maintaining such low pressure in thereturn circuit portion 2 as will always be below the pressure of thematerial passing thereto from the cross-circuits of the guns, later morefully described.

Along the line of each circuit are connected any number 'of spray gunsI6; a gun to each spray station, and each gun is connected by a.material supply duct I1, such as a hose, to the feed main I at a pointcorresponding to the spray station for that gun, and also is connectedby a material by-pass or cross-circuit duct I8, such as a hose, leadingto the return main 2 at a point also corresponding to the spray station.The gun is also connected by an air supply duct I9, such as a hose, to apressure air supply main 20, also at a point corresponding with thespraying station.

The material ducts I1 and I8 are connected to the gun II) by the meansmore fully shown in Fig. 2. This means comprises a. double portedfitting 2| to which are connected couplings 22 and 23 for the ducts I1and I8 respectively. From the fitting 2| extend pipes or tubes 24 and 25which are connected at their upper ends to the gun I6 as close aspossible to the nozzle 26 (Fig. 1) of the gun, by way of a couplingmeans 21 secured to the material inlet 28 for the gun. A chamber 29 isprovided in the coupling 21 with which communicate both tubes 24 and'25. The fitting 2| has an apertured extension 30 through which the airduct I9 may extend for connection to the air passage carried by the gunhandle 3|.

Heretofore, the material supply ducts from the supply main to the gunsconstituted dead ends when the guns were not being operated. When flowceased in such dead ends the material particles, such as the pigmentparticles, would settle in the form of sediment or the like. When a gunwas next operated the material first projected from the gun would be ofimproper characer. It was necessary for the workman to turn the gun toone side and project sufiicient material to the extent or point wherethe properly conditioned material could then be sprayed. This resultedin waste of material and time of the workman. Moreover, just when thematerial of proper condition or character arrived at the gun nozzle wasleft to the judgment of the workman who was not skilled to determinethat. Besides, since he was limited for time he would not wait longenough, and the job would be spoiled.

By the present invention the material is constantly circulating in theconnections to the gun, regardless of the gun being idle or used. Theflow is from the main I by way of the duct I1,

coupling 22, one of the passages in the fitting 2|, tube 2-4, to chamber29, and thence to tube 25, the other passage in the fitting 2|, coupling23, and duct I8 to the return main 2. By also connecting the chamberedcoupling'21 as close to the nozzle 26 as possible, there is but anegligible amount of material in the passage from the coupling 21 to thetip of the gun nozzle, and there can be no settling of the materialparticles, the passage being small. In this way, there is alwaysavailable at the gun nozzle, when the gun is operated, a homogeneousmaterial with the correct proportion of the suspended particles to thevehicle therefor.

In each supply duct I1 is connected a pressure regulating valve 32 atthe point of connection of the duct I1 with the supply main I. See Figs.1 and 5. This valve is shown in detail in Fig. 5. It so controls thepressure of the material at the gun that the material is sprayedinitially at the same pressure as during the spray interval of time sothat there is no spurt at the start of spraying.

This valve comprises a chamber 33 in which is suitably clamped a Sylphonbellows 34 having an end plate 35 acted upon by a spring 36 pressed by apressure cap 31 abutting the end of an adjusting screw 38 suitablythreaded in the upper end of the device. From the chamber 36 runs agauge passage 39 to a gauge tube 40.

The lower end of the chamber 36 has an extension 4| to which isconnected a coupling means 42. The extension has a chamber 43communicating with the chamber 36 by way of a passage 44 and directly incommunication with a chamber 45 provided in the coupling 42, the latterhaving an outlet 46 leading to the supply duct l1. In the extension 4|is provided a ported valve seat member 41 in communication witha passage48 leading from inlet 49 in which is connected a pipe or duct 58 in turnconnected to the supply main I.

To the plate 35 of the bellows is secured a rod which extends slidablyin a bored part of the extension 4| and has secured at its lower end ahub '52 of a valve retainer 53 of spider form. On the retainer 53 isfreely supported a ball valve 54 operative in a recessed lower end ofthe member 41 and adapted to control the port thereof.

As the bellows 34 contracts or expands under variations of pressure ofthe material in the chamber 33, the retainer 53 rises or fallsaccordingly to raise or lower the valve 54, so as to control the flow ofmaterial through the ported member 41. The device is so designed as notto entirely shut off the flow of material through the member 41.

By the present invention there is maintained a given pressure of thematerial at the gun, as for example fourteen pounds per square inch,regardless of the rate of flow of the material to or by the gun andirrespective of the gun being used or not used, and also indifferent tothe pressures in the main circuit portion When the pressure of thematerial at the gun tends to rise above the point to which the spring 36has been adjusted by thescrew 38, that pressure reacts by way of thepassage 46, chambers 45 and 43, passage 44 and chamber 36, so as to beeifective on the bellows 34 and thus raise the valve retainer 53 and'ball valve 54 to throttle (not to shut off) the inflow ofmaterial'through the ported member 41, thus bringing the pressure of thegun to the predetermined value. When the pressure at the gun tends todrop, as when the gun is operated to spray, immediately the bellowsexpands under the influence of the spring 36, and immediately the valve54 is moved down and more material is admitted so as to maintain thegiven pressure at the gun. The action is instantaneous and smoothwithout any vibration of the valve or the like, the action being verysensitive and within a very small fraction of a pound variation inpressure.

The cross-return duct I8 is connected to and at the return main 2 by wayof a pressure control unit 55 shown conventionally in Fig. 1 and indetail in Figs. 3 and 4. It includes a filter 56 for intercepting anyloose particle, such as a scale from the inside of the pipe, as wouldclog the control orifice 51 (Fig. 4) in the outlet part of the device,and a duct part 58 connected to the return main 2. The material flows byway of duct l6 into the device and downwardly through the filter 56, andthence through the orifice 51 which is of predetermined diameter, suchas onesixteenth of an inch, although any other size may be useddepending upon the pressure and flow conditions desired in the system-It is so designed that there will be a constant flow of the material inthe cross-circuit |1-|8, yet with no serious loss in pressure at thegun. Also, it is designed so that the pressure on the discharge side ofthe orifice 51 will always be less than the lowest pressure that will beused at the gun, such as four pounds, so that there will always be across-flow through the cross-circuit |1|8.

At the turn between the supply circuit portion and the return circuitportion 2 is provided (in l5 (Fig. 1) for controlling the pressure andflow conditions in both portions of the circuit. Also, there is a likevalve l8 in the surplusretum or feed-back line 9 to the tank 1. shown indetail in Figs. 6, 7, 8 and 9 of the drawmgs.

It comprises a chamber 59 within which is a Sylphon bellows 60 suitablyclamped at its upper end to the upper end of the device, as shown. Thebellows 6|) has a pressure plate 6| at its lower end, against which actsa spring 62 having a pressure cap 63 at the upper end of the spring andin abutment with an adjusting screw 64 suitably threaded in the upperend of the device. A tube 65 secured at its lower end to the plate 6|may surround the spring 62 to give it lateral support in case the springtends to buckle.

The lower end of the chamber 59 leads into a valve casing 66 havinginlet and outlet chambers 61 and 68 divided by a partition 69 in whichis secured, as threaded, a ported valve member 10, the chambers 61 and68 being connected to circuit ducts or remains and 2 respectively.

To the bellows plate 6| is secured a valve stem 1| which is threaded atits lower end for adjustable securement of a valve shank 12 of a valvemember 13. The valve member 13 has a cylindrical portion 14 at its upperend to fit with a closeness of a thousandth of an inch or less clearancewithin the cylindrical valve port 15 provided in the valve member 18when the valve member 1314 is moved downwardly. The valve portion 13 isprovided with one or more flats 13 (three in the illustrativeembodiment) produced by milling the cylindrical extension of the valueportion 14, the upper ends of the flats curving upwardly and radially toend in the lower circular edge of the portion 14, as shown, the verticaledges 16, so to speak, being of arc form, or arc parts of thecylindrical surface of the extension of the portion 14. Above the part14 the movable valve member may have a neck 11 and above that a conicalportion 18 the surface of which may abut the inner, upper edge 19 of thevalve member 18, so as to act as a stop for the downward movement of themovable valve assembly, if it should move down that far. The conicalpart 18 also may act as a closing seat. It is to be understood, however,that the movable valve is to move normally in a range whereby theconical part 18 will normally be always spaced away from the rim edge19. It will abut or seal only under abnormal conditions.

the illustrative embodiment) a modulating valve The neck 11 and theconical part need not be present and the shank part 12 may be of thesame diameter as the valve part 14 and be an upward extension thereof,as in the form of device shown in Fig. 9.

Heretofore, it was necessary to supply the material in the supply mainat a comparatively high pressure, such as 180 pounds per square inch, soas to allow for the maximum demand on the line, but that resulted inirregular pressures at the guns, even though pressure regulators mightbe used at the supply source with some attempt at maintaining thepressure at some normal level.

By the present invention, a much lower pressure is necessary in thesupply main, such as pounds per square inch or the like, it beingunderstood, however, that the pressure may fluctuate over a wide rangewithout affecting the proper operation of the system. This requires lesspower, and reduces the tendency to leakage at the pumps and other parts.By constantly This valve is circulating the materialandpross-circulating, and using modulating valves, the proper pressuremay be maintained regardless of variations in flow. For example, if weassume that the demand increases, the modulating valve t will act to letthrough less material to the return circult portion 2. At the same timethe modulating valve I 8, at the tanks, also will act to let 'throughless surplus or.-feed-back to the'tanks, leaving more of the materialfrom the pump to go to supply the demand. Since the modulating valveoperates on pressure factors, it will be seen that the modulating valveI5, set or adjusted for a given pressure, such as 85 pounds in thesupply main, will act to hold back, so to speak, the material at 85pounds, and only let through what material may be necessary for return.It even can substantially, but not entirely, stop how in the return,there being always some return of material by way of the cross-circuitsI'II8 irrespective of whether or not the guns are in operation.

The adjusting screw 64 of the modulating valve I5 is so adjusted as tocontrol the flow whereby there will be the given pressure, such as 85pounds in the line portion I and a given maximum, such as 4 pounds orless in the return line portion 2. Normally, there is always a. flow ofmaterial through the port 15 and the cylindrical port 88 between the rimedge 19 and the lower rim edge BI of the valve part I4, but as thepressure in the chamber 59 tends to increase the orifice 88 will bewidened and more material will flow through until the pressure returnsto the given pressure when the orifice will be narrowed to its normalopening. Likewise, when the pressure tends to drop in the line portion Ibelow the iven valve, the orifice 80 will be narrowed and less materialallowed to pass through until the pressure returns to normal and thenthe orifice 88 will widen to normal. This valve operates very quicklyand smoothly without any vibrations, and very sensitively within a verysmall fraction of a pound of pressure variation. The modulating valveII) at the tanks operates likewise.

In operation the pump 5 feeds the material under pressure by way of theduct 4 and filter 3 (or by-pass 8), to the supply circuit portion I, andto such an amount as to maintain a flow of material at given pressure inthe circuit I-2, in the cross-circuits II-IB, and the feed-back orsurplus return circuit 9, besides meeting the demand at the guns. Shouldthere be a tendency for the pressure in the line I to drop by reason ofincreased demand at the guns or otherwise, that tendency will be feltimmediately by the modulating valves I0 and I5, the former immediatelyacting to reduce the fiow' of the material to the tank 7 so that theportion of the material which would otherwise pass to the tank I will befed to the line I, and the latter, that is, the modulating valve I5,will also immediately act to reduce the flow of material to the line 2so that the portion of material which would otherwise pass to the return2 will be held back, so to speak, in the line I. Any tendency to increase the pressure in the line I will be counter.- acted by a converseaction of the valves In and I5.

While one tank 'I may be used whereby the material is drawn off at thebottom of the tank and the returning material (circuits 9 and 2) is fedback in the top of the tank, two or more nected between the v a valvedpipe 84.

tanks may be used. As for example, the material may be drawn from onetank and the returning material fed in the other tank, and when the onetank is nearly empty and the other is nearly full, suitable valves(shown conventionally as circles with crosses therein) will bemanipulated, so that the material will be drawn from the other tank, andthe returning material fed to the one tank. Other manipulable valves arealso shown conventionally by circles with crosses therein.

During the use of the device or system, besides there being a continualflow of material in the circuit I--2, there is also a continualcross-flow of the material in all cross-circuits III8,

whether or not the guns are being operated, so

that there will always be homogeneous material available at each gun atany instant the gun may be put into operation.

While the system above described is shown with the use of automaticallyoperating valves I5 and I0, respectively, at the end of the system andin the by-pass or feed-back between the pump and supply source. thesystem may satisfactorily operate with a hand operated throttle type ofvalve in the by-pass 9 if desired. How- ,ever, the use of theautomatically acting valve In is more convenient.

In a system of this kind there may be any number of various conditionsexisting at difierent instances of time, depending upon the demand madeon the volume of material for any particular job, and frequently it maybe diflicult to control the flow through each hose I'I-I8 and thepressure at each spray gun at such times when other guns are beingopened and closed.

To readily accommodate for such occurrences, the present inventioncomprehends in part the use of the back pressure regulator 55 in eachcross-circuit I'I-I8, which regulator comprises a fixed or given sizedorifice 5'! so that the flow through it will dependupon the differenceof pressures on both sides of that orifice; and in part upon theautomatic regulating valve at the end of the system with a similar valvein the bypass or feed-back 9.

In Fig. 11 is shown the end of the system provided with a pressurereducing type of valve 32*, of the same kind and construction as valve32 used in the cross-circuits I1-I8, but of larger capacity. This valve32 is connected to the circuit part I by way of valved pipes 82 and 83,the latter being connected to the inlet of the valve 32*; and isconnected to the circuit part 2 by way 0! Suitable gages may be contopipes 82-83, valve 32 and way of valved pipes 85, 86 and A valvedby-pass nected respectively return duct 2, by 81.

pipes 82 and 2, as shown in Fig. 11.

By using the pressure reducing type of valve 32 in lieu of themodulating valve l5 at the end of the system, the pressure in the returncircuit part 2 will be maintained constant instead of maintaining thepressure constant in the circuit part I on the feed side of the valve,as in the case of using the modulating valve I5. The valves 32 alsobeing of the pressure reducing type will also maintain a constantpressure in the cross-circuits I'II8. The regulator 55, which has afixed orifice 51, controls the rate of fiow of material in thecross-circuit I 'I-I8, the flow through it depending upon the differenceof pressures on the two sides of theback pressure regulator 55. If thepressure in the hose I8 changes there will also pipe 88 may also beconthe flow of material through all cross-circuits be a change in volumeof material discharged into the return circiut part 2, which in turnwill produce or tend to produce a variation in pressure.

be accomodated for by the valve 32 acting to .change the pressure backto that predetermined by the setting of the \lva 82. Also, there will bea tendency to vary the pressure at the gun, but this will also beimmediately accommodated for by the valve 32 acting to change thepressure back to that predetermined by the setting of the valve 32. Inother words, there is an automatic balancing occurring when there is avariation of demand on the system. i

To illustrate, the modulating valve In in the feed-back 8 may be set sothat material supplied to the supply circuit part I will have apressuretherein of forty pounds when all the guns are opened, and a pressure ofsixty pounds when all the guns are closed. The valve 32' will be so setas to maintain a pressure of say twenty pounds in the return circuitportion 2 for paints oi average viscosity. The regulating valves 32 maybe set at thirty pounds so that they will properly opcrate with higherpressures in the line I, as be-= tween forty and sixty, regardless ofthe variations in pressure in such range, or even of higher pressures.It the pressure in line i should rise above that (sixty) then themodulating valve it acts to feedback more material so as to bring downthe main line pressure.

The back pressure regulator 55, in such case, would have the orifice 5101 such size as to maintain the desired flow of material through thecross-circuit "-48 and also maintain what might be termed the balance ofpressures on both sides of the regulator 55. Assuming that as many astwelve guns are opened, pressures in the line I may drop from sixty toforty-five pounds, but the pressure at the uns will not vary; it willremain constant.

In operation, when a gun is opened the valve 32 immediately acts to passmore material to the gun circuit Il-|8, effecting a slight drop inpressure in the line part I. Modulating valve ll immediately acts toreduce the feed-back, so'that some of the material that would beotherwise bypassed is now fed into the main line I. Since there is aslight reduction in the material returned to the line part I, when thegun is opened, the pressure in the return 2 will tend to fall slightlyand the valve 32 will open slightly to make up for this and bring thepressure in the return line 2 back to the predetermined value. As moreguns are opened, this process is repeated and the pressure in the mainline I will continue to drop until it reaches the minimum (such as iortypounds) when all guns are open.

From tests conducted with pressure values as given above, by way ofexample, it was found that there was no variation of pressure in thereturn line 2 as the guns were opened or closed.

The pressure in the supply line I fell steadily as l|-I8, it is onlynecessary to raise or lower. respectively, the setting of the valve 32'whereby the pressure across the back pressure regulators 55 will bechanged and the flow therethrough varied as desired.

When spraying materials that are desired to be applied hot, or which byreason of their properties are more easily sprayed when hot, heatingmeans may be used to supply the desired temperature to the material. InFig. 10 is conventionally shown a fragment of the system including across-circuit II--I8, the circuit part II of which is enclosed in andpasses through a jacket 89 having inlet and outlet ducts 90 and ill forthe flow of the heating fluid or medium through the jacket and aroundthe enclosed section of the duct II, this part of the duct I! beingpreferably a pipe instead of a hose. When heating is used, it isdesirable to return the material from the return pipe 2 directly to theintake oi the pump instead of to the tanks i, such direct return beingby way 0! the valved duct M. This is preferable to prevent the es-= capeoi thinners which might occur it the me. terlal were fed back to thetanks 7. Also, with material of this hind, it is desirable not tomaintain it hot too long before using, so by returning it directly tothe pump, the material in the tanks 7 is supplied to the line formake-up" only as the material is consumed, whereby the amount beingheated is considerably reduced.

The medium used in the heaters 89 may be at about 1m) F. so that thetemperature of the material may be maintained at about F. Thus, thematerial will not be dangerously or iniuriously overheated even thoughit should flow very slowly through the heater or even stand in theheater for some time.

The invention is not limited to the use of the pressure and temperaturevalues given herein, such values being referred to only by way ofexample.

While we have herein described and upon the drawings shown anillustrative embodiment of the invention, it is to be understood thatthe invention is not limited thereto but comprehends otherconstructions, arrangements of parts, de tails, features, or the like,without departing from the spirit of the invention.

Having thus disclosed the invention, we claim:

1. A distributing and circulating system for liquid material comprisinga main circuit means including supply and return circuit portions, amaterial applying device, a cross circuit portion including inlet andoutlet ducts respectively connected to said supply and return circuitportions and both connected to said device, a valve connected to saidinlet duct and provided with means responsive to the pressure in saidinlet duct for controlling the volume of liquid flow from said supplycircuit portion to said inlet duct inversely to the pressure in saidinlet duct, and a flow control means connected to said outlet duct andincluding a constantly open passage of such restricted size that thepressure therein is always less than that at the material applyingdevice.

2. A distributing and circulating system for liquid material comprisinga circuit means including main supply and return circuit portions, meansfor supplying liquid under pressure to said main supply portion, one ormore spraying devices, one or more cross circuit means respec tively forsaid devices, each cross circuit means connected to said main supply andreturn circuit portions and both connected to the respective sprayingdevice, means in said discharge duct provided with a constantly opendischarge orifice of predetermined restricted cross sectional area foreffecting a pressure at the discharge side of the orifice lower than thelowest pressure acting at the spraying device, and means in the supplyduct for controlling the flow of liquid to said supply duct andincluding means responsive to the pressure in the supply duct forvarying said flow inversely with said pressure in said supply duct.

3. A distributing and circulating system for liquid material comprisinga main circuit means having supply and return circuit portions, meansfor supplying liquid under pressure to said main circuit means forcontinual flow of liquid material therein, a cross circuit meansconnected 2,244,686 i including supply and discharge ducts respectivelyto said supply and return circuit portions for continual flow of liquidmaterial therein. a material applying device connected to said crosscircuit means, a liquid flow control means in said cross circuit meansbetween said material applying device and said supply circuit portionand having an opening for continual flow of liquid therethrough, meansresponsive to the pressure in said cross circuit for varying the size01' said opening for varied flow of material inversely proportional tothe pressure in the cross circuit, and means in said cross circuitbetween said material applying device and said return circuit portionand having an opening of given restricted constant size for continualflow of material therethrough to said return circuit portion.

FREDERIC G. GARRISON.

ALFRED W. CHRISTENSON.

